The present invention relates to a process and apparatus for drying polymeric material to be melted and utilized to form polymeric articles.
Dryers including drying hoppers have been utilized in the plastics industry for years. These dryers provide heated, dehumidified air to a drying hopper. Polymeric material, e.g., resin pellets, contained in the drying hopper are exposed to the heated, dehumidified air such that moisture is removed from the pellets. If moisture is not removed from the surface and interior of the pellets before the pellets are melted and formed into parts, the quality of resulting parts may be unacceptable.
Thus, the amount of time polymeric material remains in a drying hopper before being delivered to one or more processing machines located downstream from the dryer can impact the quality of parts formed by the processing machines. If polymeric material remains in the drying hopper too long, it may degrade. If polymeric material leaves the drying hopper too soon, wet material reaches the processing machines which, as noted above, can adversely impact the quality of parts formed by the processing machines.
There is a need for an improved control system which is capable of causing polymeric material to be delivered to a drying hopper at approximately the same rate at which material is actually removed from the drying hopper.